Flash lamp



Aug. 15, 1950 D. J. JONES EI'AL 2,519,252

FLASH LAMP Filed Aug. 1, 1947 lnvenTors David John Jones, S'l'onle V. Williams, Decd. 33 Fro nzz/es Mabel Williams, Exrx.

Their ATTor-neg Patented Aug. 15, 1950 FLASH LAMP David John J ones. Wembley, England, and Stan-- ley Vaughan Williams, deceased, late of Kenton, England, by Frances Mabel Williams, executrix, Kenton, England, assignors to General Electric Company, a corporation of New York Application August 1, 1947, Serial No. 765,580 In Great Britain March 27, 1946 Claims. 1

Our invention relates to flash lamps of the type comprising a sealed envelope containing an oxygenous atmosphere and combustible material adapted when ignited to burn rapidly in the said atmosphere so as to produce a momentary flash of actinic light. More particularly, our invention relates to a combustible material for such lamps, and to the manufacture thereof. The combustible material is usually adapted to be ignited by the passage of an electric current either through thematerial itself or through a primer whose combustion, produced thereby, serves to ignite the combustible material. The present application is a continuation-in-part of our co-pending application Serial No. 742,116, filed April 17, 1947, now abandoned, and assigned to the assignee of the present application.

Flash lamps of the above mentioned type are used primarily for photographic purposes and it is known that from the point of view of its combustion properties, one of the most desirable materials for such use is magnesium, which burns easily and rapidly, emitting light of high intensity and having good actinic properties. But

magnesium and the magnesium-rich alloys proposed hitherto for such use are dlfllcult to work mechanically except possibly at elevated temperatures, and it is not easy to obtain them in the form of fine wire or thin foil, in which form it has been found advantageous to provide the combustible material in flash lamps of the type specified. Accordingly, magnesium and magnesium-rich alloys have not been used as extensively as their good combustion properties would indicate.

it is an object of our invention to provide a novel combustible material for flash lamps of the above-mentioned character.

Another object of our invention is to provide a metallic material which is comparatively easy to work mechanically at room temperature, which can be readily obtained in the form of fine wire or thin foil, and which is very suitable for use as the combust ble material in flash lamps of the type specified.

We have found that by the addition of a certain amount of lithium to magnesium, an alloy is obtained which possesses all of the above described properties. The essential feature of the alloy, to insure good mechanical working properties, is that sufficient lithium should be present to insure that all or the greater part of the alloy is of the 5 phase having a cubic structure, rather than the a phase which has a hexagonal structure.

7 content increases.

Further features and advantages of our invention will appear from the following detailed description of a species thereof and from the accompanying drawing in which the single figure is an elevation of a flash lamp embodying the invention.

Referring to the drawing, the flash lamp there illustrated is of the usual type comprising a sealed envelope or bulb I, of light-transmitting material such as glass, having a re-entrant stem 2 provided with a, press portion 3. Within the bulb l is a filament 4 electrically connected to and supported by a pair of lead-in wires 5, t which are sealed through the press portion 3 of the stem 2 and are electrically connected to the terminals of a base i secured to the neck of the bulb. The lead-in wirer 5, 6 are provided with small beads 8 of a, suitable fulminating substance, for instance, a mixture of finely-divided magnesium, zirconium and an oxidizing agent such as potassium perchlorate, bonded together by a suitable binder such as a 4 to 5 per cent solution of nitrocellulose The beads 8 are disposed on the lead-in wires 5, 6 at the point where the filament 4 is connected thereto so as to be in contact with the filament. The said beads 8 constitute, together with the filament t, the igniter or primer for the lamp. Disposed within and loosely arranged in the bulb l' is a quantity of approximately uniform thin-section solid combustible or flasher material 9 according to the invention, which may be in the form of line wire or thin foil. The bulb is fllled with a gaseous filling such as oxygen or an oxygen containing gas at a suitable pressure.

p In accordance with the invention, at least a substantial part of the combustible material 9 consists of a magnesium-lithium alloy in the form of a flne wire or thin foil, the lithium content of the alloy being such that all or the greater part of the alloy is of the 5 phase having a cubic structure. Since the combustion properties of the lithium are not as good as those of the magnesium it is desirable to keep the lithium content as small as possible; on the other hand the working properties of the alloy improve as the lithium We have found it desirable to keep the lithium content within the range, by weight, of 8%-16% of the weight of the magnesium and we prefer to use a content of about 12% by weight.

To -obtain the best cold working properties the magnesium and lithium should both be of high purity.

The statement that the metal consistsof a magnesium-lithium alloy does not exclude the possibility of the presence of a small quantity of one or more other metals, such as cadmium or beryllium, which may be added to the alloy to improve still further its mechanical working properties; thus with the preferred magnesiumlithium composition aforesaid we have found it desirable to add up to by weight, of the whole, of cadmium and from 1-2% by weight, of the whole, of beryllium. Such additives should also be of high purity.

It will be understood that the term thin foil includes thin strips, ribbons and the like as well as sheets of foil.

One method of manufacturing the combustible metal for use in accordance with the invention will now be described by way of example.

Weighed quantities of the magnesium and lithium, together with any other metal additives which may be used, such a cadmium or beryllium, are placed in a soft iron crucible which is then suspended inside a Briinweld type pot having the usual water-cooled rubber gasket seal. After bolting down the pot head, through which run connections to a vacuum pump and argon supply, the pot is evacuated to a pressure of about mms. mercury and then filled with pure argon.

The pot is then heated within an electric resistance furnace to'about 900-950 C. and held at-this temperature for about half an hour, the melt being allowed to boil at least once, preferably twice, during this period by evacuating the pot and subsequently refilling with argon.

The pot is then removed from the furnace, usually by withdrawal of the furnace from around the pot, and the molten alloy allowed to cool down to room temperature within the pot, so as to solidify from the bottom of the crucible upward tOfiVOld piping, with the pot either evacu ated or filled with argon.

The solidified ingot is then removed from the pot and separated'from the crucible, after which the ingot is homogenized by heating to about 400 C. for about 8 hours in a furnace which is either evacuated or filled with argon. The ingot is then ready for working.

The ingot is first hot rolledat about 350 C. to form a rod about cm. square in cross-section, and isthen cold rolled and drawn into wire of about 1 mm. square cross-section, with intermediate anneals, at 300-325 C. in a vacuum or argon atmosphere, after approximately every 50% reduction in area.

The wire is then further reduced in diameter by cold nrawing with intermediate anneals, at 300-325 C. in a vacuum or argon atmosphere, after approximately 60-70% reduction in area until a sufliciently fine wire, for example 0.05

mm. diameter, is obtained.

4 If required, this fine wire can be formed into thin strip; by cold rolling, or 'the larger diameter wire can be cold rolled into foil and then 2. In a flash .lamp, a combustible comprising i a solid approximately uniform thin-sectioned material of an alloy consisting essentially of magnesium and lithium and lithium, the lithium content amounting to about 12% by weight.

3. In a flash lamp, a combustible comprising a solid approximately uniform thin-sectioned material of an alloy consisting essentially of magnesium and from 8 to 16 per cent by weight of lithium and containing a small amount not exceeding 5 by weight of cadmium.

4. In a flash lamp, a combustible comprising a solid approximately uniform thin-sectioned material of an alloy consisting essentially of magnesium and from 8 to 16 per cent by weight of lithium and containing from 1%2% by weight of beryllium.

5. A flash lamp having as a combustible a quantity of solid approximately uniform thinsectioned combustible material of an alloy consisting essentially of magnesium and lithium, the lithium being present in an amount ranging by weight from 8%-l6% of the weight of the magnesium.

DAVID JOHN JONES. FRANCES MABEL WILLIAMS, Executria: of the Estate of Stanley Vaughan Williams, Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Henry et al.: Institute of. Metals A. I. M. E., vol. III, 1934; pages 319-332.

Hume-Rothery et al.: J. Institute of Metals, vol 71, 1945, pages 589-601.

Div.

Certificate of Qorrection Patent No. 2,519,252 August 15, 1950 DAVID JOHN JONES ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 16, strike out the Words and lithium, first occurrence;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofice.

Signed and sealed this 24th day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents.

Certificate of Correction Patent No. 2,519,252 August 15, 1950 DAVID JOHN JONES ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 16, strike out the Words and lithium, first occurrence;

and that the said Letters Patent should he read as corrected above, so that the same may conform to the record of the case in the Patent Ofice.

Signed and sealed this 24th day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

